[GHC] #16104: Plugin name lookup behavior change from GHC 8.4 series

[GHC]

#16104: Plugin name lookup behavior change from GHC 8.4 series
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        Reporter:  lerkok            |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.6.4
       Component:  Compiler          |              Version:  8.6.3
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"0d9f105ba423af4f2ca215a18d04d4c8e2c372a8/ghc"
 0d9f105b/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="0d9f105ba423af4f2ca215a18d04d4c8e2c372a8"
 GhcPlugins: Fix lookup of TH names

 Previously `thNameToGhcName` was calling `lookupOrigNameCache` directly,
 which
 failed to handle the case that the name wasn't already in the name cache.
 This
 happens, for instance, when the name was in scope in a plugin being used
 during
 compilation but not in scope in the module being compiled. In this case we
 the
 interface file containing the name won't be loaded and
 `lookupOrigNameCache`
 fails. This was the cause of #16104.

 The solution is simple: use the nicely packaged `lookupOrigIO` instead.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16104#comment:12>
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